In order to understand the biological function of protein-lipid complexes such as serum lipoproteins as well as the factors governing abnormal lipid association products such as sclerotic plaques on arterial walls, it is essential to define the assembly process in thermodynamic terms. The principal objectives of this proposal are to determine whether or not lipoproteins are self-assembling according to thermodynamic laws and to define the interactions governing lipid, sterol, and steryl ester distributions among circulating serum lipoproteins and other biological entities (i.e. atherosclerotic plaques, cell membranes, etc.).